The problem with the combustion of ammonia is its inertness. Therefore, an interesting approach is the preliminary partial conversion of ammonia to hydrogen, so that a suitable reactivity is achieved by mixing NH₃ with small amounts of H₂. This results in research questions concerning the combustion properties of NH₃ as a function of the H₂ content, laminar and turbulent burning velocity, flame stability limits and pollutant emissions under different pressures.

The direct use of ammonia in energy and transport systems is challenging due to the difficult combustion behavior as well as emissions of nitrogen oxides (NO_x, N₂O) and unburned ammonia. A promising solution to these problems is the preliminary partial cracking of ammonia. In order to gain a better understanding of the combustion properties of these cracked ammonia mixtures and “impure” ammonia, including the flame behavior and external ignition as well as the emission profiles, this project will comprehensively investigate the reaction kinetics of the fuels, both experimentally and theoretically.

The project will develop numerical simulation methods for ammonia-hydrogen combustion using a CFD solver. New kinetic reaction mechanisms to describe the flame stability and the formation of pollutants, especially NO_x, N₂O and unburned ammonia, are needed to facilitate predictive and computationally feasible simulations. The data on the reactivity of the NH₃ mixture with partially released H₂ and the flame ignition will be used to determine the relevant operating conditions. The simulations are validated against experimental data for a range of different mixtures, from 100% H₂ to 100% NH₃.

This project aims to synthesize novel types of electrocatalysts free of precious metals for use in low-temperature direct ammonia fuel cells for the ammonia oxidation reaction (AOR). As possible material classes for the electrocatalysts, transition metals on carbon and metal-nitrogen-carbons (M-N-C catalysts) will be selected and investigated.

Integrating the endothermic reaction for the conversion of NH₃ in oxide ceramic high-temperature fuel cells (HT-DAFC) for direct electrochemical utilization requires a reliable prediction of the temperature profile and the reaction current density along the flow field. Based on an existing model for fuels used so far (hydrogen, methane, methanol), the project aims for a two-plus-one-dimensional modeling of a solid oxide fuel cell directly supplied with NH₃.

In this project, diagnostic investigation methods are applied to the low-temperature direct ammonia fuel cell (DAFC). The aim is to determine the individual contributions of the overvoltages due to the kinetics (in particular the ammonia oxidation reaction, AOR) as well as the charge and electron transport processes at cell level. A better understanding of the processes in the cell and at the electrode-electrolyte interface will enable a long-term improvement in the power densities of LT-DAFCs.

The objective of this project is to identify and implement innovative thin-film catalysts for the low-temperature DAFC. For this purpose, catalyst layers are applied directly by magnetron sputtering to a gas diffusion layer for the production of a gas diffusion electrode (GDE) in order to realize very low and efficiently used catalyst loadings. The focus will be on the ammonia oxidation reaction (AOR), for which common precious metal thin-film catalyst materials will initially be produced and characterized from a materials science and electrochemical perspective.